Year	% of revenue
1972	4.6433990895295905
1973	4.731182795698925
1974	4.96675791943684
1975	5.243820975283901
1976	4.738341580446844
1977	8.027372022634557
1978	6.252791424743188
1979	4.933110367892977
1980	3.292123906098069
1981	4.47798428339778
1982	4.880462524089797
1983	3.263767582973246
1984	2.496789302712095
1985	2.8945700401436723
1986	3.754501165007414
1987	3.794912264413704
1988	5.895876594482349
1989	8.805430613427523
1990	3.61238756036918
1991	3.7166720952957055
1992	2.3282782224924286
1993	3.5090531874764244
1994	1.6978233034571064
1995	4.11141162100855
1996	3.8361221962324255
1997	2.5273563358744733
1998	2.6440691492014725
1999	2.615641778993677
2000	2.958826061115324
2001	2.7372009522555576
2002	2.7336946003483646
2003	2.3561698723850575
2004	3.256250109695035
2005	3.829822293203539
2006	4.228108977943909
2007	4.120966999495996
2008	3.155259499503707
2009	2.663355366338811
2010	3.3953641762772784
2011	3.8813533615329376
2012	4.071586760907801
2013	4.118767945974644
2014	3.370364630339721
2015	3.4884202865833096
2016	3.2649826086323213
2017	3.3946263162926407
2018	3.657186088931854
2019	3.3933220595628066
2020	2.9892896055905105
2021	3.1470681084151844
2022	3.725662699367528